Opiate receptors mediate the pharmacological action of morphine-like drugs and probably serve as post-synaptic membrane receptors for a new class of morphinergic neurons, which manufacture a morphine-like neurotransmitter substance called enkephalin or anodynin. Experiments in this laboratory which are aimed at elucidating the role played by these neurons in normal brain function include: 1) determination of structure activity relationship of synthetic enkephalin analogues and affinity for opiate receptors, 2) production of antibodies to enkephalin for visulization and mapping or morphinergic neuron brain distribution, 3) analysis of receptor-mediated ionic conductance changes elicited by opiates, 4) analysis of opiate effects on brain cyclic nucleotide production.